What are they?

X-Rays are a type of high energy electromagnetic wave. As shown below, they have the second highest frequency and therefore shortest wavelength of the standard types of wave in the spectrum. X-rays can be generated by machines and are naturally given off by stars and other objects. As many objects in the universe emit x-rays they are used by astronomers to detect items that could otherwise not be seen as clearly.
Dictionary definition: ''A type of radiation (energy in movement) that can go through many solid substances, allowing hidden objects such as bones in the body to be photographed.''

This shows how high the frequency of X-Rays is
This shows how high the frequency of X-Rays is

Are they dangerous?

X- rays can damage cells and cause cause cell mutation which can cause cancer or cell death. It can cause these illnesses as it produces radiation as do lots of high frequency waves, this causes cells to behave differently and can have severe effects. Ironically X-Rays are also used to treat cancer, this treatment is called radiotherapy, it involves a very high amount of radio waves. People are X-Rayed fairly regularly and although the process is safer than it used to be there is still a relatively high risk of becoming ill as a side effect of the treatment.

Type of X-Ray
Minimum Risk of cancer
Maximum Risk of cancer
Chest, Teeth, Arms or Feet
Not Available
-1 in 1,000,000
Skull or Neck
1 in 1,000,000
1 in 100,000
Mammogram,hip, spine,abdomen or pelvis
1 in 100,000
1 in 10,000
Barium meal
1 in 10,000
1 in 1,000
Source : NHS (http://www.nhs.uk/conditions/x-ray/Pages/Risks.aspx)

Where do they come from?

X-rays are generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high speed, they can be produced many different ways to produce different frequencies of wave that can be used to see through different objects. They are produced in parcels of energy called photons. They are also produced naturally by many objects in the universe, scientists use these to work out what far away objects are.

This is a typical hospital X-Ray machine
This is a typical hospital X-Ray machine

How do we detect them?

In hospitals the pictures were captured using image receptors such as thin films and photographic plates. Now they use computer technology to generate the images produced by X-Rays. Astronomers also use X-Rays, as these are absorbed by the earth's atmosphere they use balloons and satellites at very high altitudes. X-Rays can be indirectly sensed by humans but they cannot be seen by any human or animal eye.

What can they be used for?

X- rays can be used to look at the internal structure of objects, they are often used in airport scanners as they can travel through fairly thick objects without being scattered or absorbed. This makes them very good at producing normally images of normally opaque objects, they can also be used to check for weak spots in metals. The idea of using X-Rays to see through human tissue was first formulated in 1895 in Germany. Dentists use them very often to get a more detailed image of the inside of the mouth, they can check for any chips or cavities much more easily than looking manually,especially right at the back of the mouth.

Other facts

  • High energy X-Rays are used to scan bones as they will pass through other tissues however if a low-energy X-Ray is used it will not pass though these softer tissues, this is why low-energy X-Rays are used for brain scans.
  • Patients can be given what is known as a 'Barium meal' before X-rays, this is a Barium Sulphate substance that will absorb X-Rays, this means that a patient's digestive system will show up clearly on an X-Ray image.
  • They are called X-Rays because when Rontgen (the scientist who first discovered them) first started to investigate them he found it very difficult to understand their nature. In mathematics the letter x means an unknown value so he used x to mean something that was not yet explained by science.
  • There a few types of tropical fish that are known as X-Ray fish as they are almost transparent but the cavity of their bodies can been seen.

A hospital X-Ray picture.
A hospital X-Ray picture.

The Eye

Main Parts

  • Iris: it is the pigmented part of the eye, it controls how much light enters the eye. The muscles expand and contract to change the size of hole or pupil at the centre of the eye.
  • Cornea: It is the outer coating on the eye, hard and transparent, its convex shape bends light that comes into the eye.
  • Lens: It is a bi-concave flexible dics that sits behind the iris, its function is to focus light onto the retina, as you can see on the diagram is attached by the suspensory ligaments to the ciliary muscle.
  • Retina: This is the lining at the back of the eye which contains light receptors, it contains two types of cells- rods which are sensitive to shape and cones which are sensitive to colour. The small section in the middle of this contains a large concentration of cones.
  • Optic Nerve: A large collection of sensory neurones (nerve cells) at the back of the eye which send the images that are collected by the retina to the brain.

A diagram of the human eye
A diagram of the human eye


Light enters the eye and is bent, magnified,focused and flipped by different parts to make the clearest image possible. The light that we can see is classed as visible light on the electromagnetic spectrum, the range in frequency in this section of the spectrum can be detected by the eye as a range of colour.

How are they generated?
They are made by stars,supernovas,black holes and pulsars. They are also created on earth by lightning and nuclear explosions.
An X-Ray tube or objects in space.
The main producer of these rays is the sun however man made lamps can also be used to create stronger, more concentrated rays.
This can begenerated in many different ways, almost always connected with heat our largest source of light in the sun.
Lots of objects produce infared energy, anything living or warm will produce a certain amount.
They are emitted from large stars and in mobiles they are made with a transmitter chip and an antenna.
They are made naturally by lightning and astronomical objects but can be man'made by transmitters.
How are they detected?
Using gamma ray detectors, they use crystal blocks which collide with the elecrons in the rays. The most common instrument used to detect them is a geiger meter.
Satellites or image receptors such as thin films or photographic plates.
Simple filters are used as well as more expensive detectors.
Our eyes detect light, we interpret different wavelengths of light as different colours.
We cannot see these rays but things like night-vision goggles and secial detectors can allow us see warm objects emitting this type of energy.
We use receivers if they are used in mobile phones.
They are detected using radio telescopes. Antenas are used to detect specific wavelengths but can only pick up a veryn limited portion of the whole range of waves.
How might they be dangerous?
They are dangerous as they are radioactive but can be used to cure cancer. Radiation is extremly harmful even in very small doses, this is why anyone working with substances that produce radiation will wear full hazmat suits to protect themselves.
The radiation can cause cell mutilation which is often a cause of cancer.
The rays kill cells leaving skin readened- we call this sunburn. Although this effect does disappear after a while the lasting damage is very likely to cause things like skin cancer.
An excess of light can cause temporary or permanent blindness and the heat connected with it can cause burns but at a normal level visible light is harmless.
Infared waves are heat waves, to much heat will damage or kill cells causing burns.
Prolonged exposure can damage the cataracts, they can also cause blindness. Workers on aircraft carrier decks wear suits to protect themselves from being fryed by the radar machines.
High exposure to radio waves is thought to cause cancer. Normal radio waves have a fairly low frequency so are not harmful although some people claim that their health has been affected by overhead cables near their homes.
What are the main or most significant uses?
They can be used to study mutations in cells such as cancer and are also used like X-Rays.
To scan for bone breakages or in dentists.
The rays are used for tanning although this is very dangerous. They are used to kill bacteria in labs, working out what things are made of and the structure and density of atoms.
We use light to sense what is around us, it enables us to see objects and generally survive.
These can be used for cooking in grills and toasters and are what a TV remote uses to change channels.
They are used mainly for heating up food and in mobile phones.
They can be used in astronomy to detect how far objects are away and if they emitt waves these can be analysed. Man made waves have beeen used for a long time to send and recieve signals and images, now they are used in radios, phones,televisions and radar and wireless computer systems.

Impressive work. The section on X rays has been populated and presented with intelligence, and will be of great help to others.
Grade A, with a merit.

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